Name of the movement of a wheel

I have searched the net and i cannot find the answer, i know i have only just read it but i cant remember where.

Basically all i want to know is the name of the movement of a while when it is moving a vehicle (i dont mean around in a circle, it's the one where it arches over on each movement, like crawling when you drag your arms back, they remain still but your body moves forwards).

Also can you show me a website that explains it? Just the website that explained would be fine but if you can explain it here i will be more than grateful.

Petrushka, I believe the curve you are looking for is a cycloid. A cycloid is the path traced out by a point on the circumference of a moving wheel. For points inside and outside the wheel, you get epi- and hypo-cycloids.